Lee Silverman

Human T-Cell Lymphotropic Virus Type 1 Open Reading Frame II-Encoded p30II Is Required for In Vivo Replication: Evidence of In Vivo Reversion

ABSTRACT Human T-cell lymphotropic virus type 1 (HTLV-1) causes adult T-cell leukemia/lymphoma and exhibits high genetic stability in vivo. HTLV-1 contains four open reading frames (ORFs) in its pX region. ORF II encodes two proteins, p30II and p13II, both of which are incompletely characterized. p30II localizes to the nucleus or nucleolus and has distant homology to the transcription factors Oct-1, Pit-1, and POU-M1. In vitro studies have demonstrated that at low concentrations, p30II differentially regulates cellular and viral promoters through an interaction with CREB binding protein/p300. To determine the in vivo significance of p30II, we inoculated rabbits with cell lines expressing either a wild-type clone of HTLV-1 (ACH.1) or a clone containing a mutation in ORF II, which eliminated wild-type p30II expression (ACH.30.1). ACH.1-inoculated rabbits maintained higher HTLV-1-specific antibody titers than ACH.30.1-inoculated rabbits, and all ACH.1-inoculated rabbits were seropositive for HTLV-1, whereas only two of six ACH.30.1-inoculated rabbits were seropositive. Provirus could be consistently PCR amplified from peripheral blood mononuclear cell (PBMC) DNA in all ACH.1-inoculated rabbits but in only three of six ACH.30.1-inoculated rabbits. Quantitative competitive PCR indicated higher PBMC proviral loads in ACH.1-inoculated rabbits. Interestingly, sequencing of ORF II from PBMC of provirus-positive ACH.30.1-inoculated rabbits revealed a reversion to wild-type sequence with evidence of early coexistence of mutant and wild-type sequence. Our data provide evidence that HTLV-1 must maintain its key accessory genes to survive in vivo and that in vivo pressures select for maintenance of wild-type ORF II gene products during the early course of infection.

Human T-lymphotropic virus type-1 p30 alters cell cycle G2 regulation of T lymphocytes to enhance cell survival.

BackgroundHuman T-lymphotropic virus type-1 (HTLV-1) causes adult T-cell leukemia/lymphoma and is linked to a number of lymphocyte-mediated disorders. HTLV-1 contains both regulatory and accessory genes in four pX open reading frames. pX ORF-II encodes two proteins, p13 and p30, whose roles are still being defined in the virus life cycle and in HTLV-1 virus-host cell interactions. Proviral clones of HTLV-1 with pX ORF-II mutations diminish the ability of the virus to maintain viral loads in vivo. p30 expressed exogenously differentially modulates CREB and Tax-responsive element-mediated transcription through its interaction with CREB-binding protein/p300 and while acting as a repressor of many genes including Tax, in part by blocking tax/rex RNA nuclear export, selectively enhances key gene pathways involved in T-cell signaling/activation.ResultsHerein, we analyzed the role of p30 in cell cycle regulation. Jurkat T-cells transduced with a p30 expressing lentivirus vector accumulated in the G2-M phase of cell cycle. We then analyzed key proteins involved in G2-M checkpoint activation. p30 expression in Jurkat T-cells resulted in an increase in phosphorylation at serine 216 of nuclear cell division cycle 25C (Cdc25C), had enhanced checkpoint kinase 1 (Chk1) serine 345 phosphorylation, reduced expression of polo-like kinase 1 (PLK1), diminished phosphorylation of PLK1 at tyrosine 210 and reduced phosphorylation of Cdc25C at serine 198. Finally, primary human lymphocyte derived cell lines immortalized by a HTLV-1 proviral clone defective in p30 expression were more susceptible to camptothecin induced apoptosis. Collectively these data are consistent with a cell survival role of p30 against genotoxic insults to HTLV-1 infected lymphocytes.ConclusionCollectively, our data are the first to indicate that HTLV-1 p30 expression results in activation of the G2-M cell cycle checkpoint, events that would promote early viral spread and T-cell survival.

Paratrichial sweat gland adenocarcinoma in a marmoset.

ical characterization of hemangiopericytomas and other spindle cell tumors in dog. Vet Pathol 33:391–397. 13. Porter PL, Bigler SA, McNutt M, Gown AM: 1991, The immunophenotype of hemangiopericytomas and glomus tumors, with special reference to muscle protein expression: an immunohistochemical study and review of the literature. Mod Pathol 4:46–52. 14. Postorino NC, Berg RJ, Powers BE, et al.: 1988, Prognostic variables for canine hemangiopericytoma: 50 cases (1979– 1984). J Am Anim Hosp Assoc 24:501–509. 15. Pulley LT, Stannard AA: 1990, Tumors of the skin and soft tissues. In: Tumors in domestic animals, 3rd ed., pp. 48–51. University of California Press, Berkeley, CA. 16. Rabanal RH, Fondevila DM, Montane V, et al.: 1989, Immunocytochemical diagnosis of skin tumours of the dog with special reference to undifferentiated types. Res Vet Sci 47:129–133. 17. Richardson RC, Render JA, Rudd RG, et al.: 1983, Metastatic canine hemangiopericytoma. J Am Vet Med Assoc 182:705– 706. 18. Schurh W, Skalli O, Lagace R, et al.: 1990, Intermediate filament proteins and actin isoforms as markers for soft-tissue tumor differentiation and origin. III. Hemangiopericytomas and glomus tumors. Am J Pathol 136:771–786. 19. Stefansson K, Wollmann R, Jerkovic M: 1982, S-100 protein in soft-tissue tumors derived from Schwann cells and melanocytes. Am J Pathol 106:261–268. 20. Yager JA, Wilcock BP: 1994, Color atlas and text of surgical pathology of the dog and cat: dermatopathology and skin tumors. Wolfe Publishing, London, England. 21. Yoshihara T, Nagai K: 1997, Infantile schwannoma of the maxillary sinus. Intern J Ped Otorhinolaryngol 40:181–187.

Human T-Lymphotropic Virus-Associated Neurological Disorders

Human T-cell lymphotropic virus type 1 (HTLV-1), the first human retrovirus discovered, has a tropism for T lymphocytes and has been established as the causative agent of adult T-cell leukemia/lymphoma (ATLL), an aggressive CD4 T-cell malignancy (1, 2, 3, 4). HTLV-2 was subsequently isolated and found to share approximately 60% nucleotide sequence homology with HTLV-1 (5). In the mid-1980s, HTLV-1 began to be associated through epidemiologic studies as a contributing factor in chronic neurodegenerative disorders. These clinical syndromes were first reported in Japan and Martinique (French West Indies), both regions that were endemic for HTLV-1 infection (6,7). Through important international cooperative studies, both syndromes were revealed to be identical in clinical presentation and are now known collectively as HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). HTLV-2 has been sporadically associated with lymphoproliferative diseases and recently has been implicated in isolated case reports of neurological disease (8,9).